Fishing barometer — how pressure shapes the bite.

Today's bite score — Sydney

The Fishare bite score incorporates barometric pressure trend alongside tide, wind, water temperature and solunar timing. A score above 70 means multiple favourable factors are aligned.

Pressure trend → bite guide

The rule of thumb used by most experienced anglers — validated by the Fishare training data across approximately 2.5M catch records:

The science — swim bladder and pressure sensing

Most bony fish (teleosts) have a gas-filled swim bladder — a buoyancy organ they inflate or deflate to remain neutrally buoyant at a given depth. The swim bladder is sensitive to external pressure change: when the barometer drops rapidly, the external water pressure decreases and the swim bladder gas expands, creating discomfort. Fish respond by moving shallower and feeding aggressively before conditions worsen.

Cartilaginous fish — sharks, rays, and skates — do not have swim bladders and are therefore less responsive to barometric change. This is why sharks can be caught reliably in almost any barometric condition.

The Fishare forecast model captures this by ingesting hourly pressure readings and calculating the 12-hour pressure trend as one of 27 input features to the bite-score model.

Frequently asked questions

• What is a fishing barometer?
  A fishing barometer is a tool (or a forecast feature) that tracks barometric pressure to predict fish feeding activity. Fish sense pressure changes through their swim bladders, which are gas-filled organs that maintain neutral buoyancy. When pressure drops rapidly, the swim bladder expands slightly, causing discomfort that fish respond to by feeding aggressively before the front arrives. When pressure rises steadily after a front, fish become more active and feed reliably.
• What barometric pressure is best for fishing?
  Rising pressure after a front is generally the best condition for sustained fishing. The 12–24 hours following a cold front, as the barometer climbs back toward 1013–1025 hPa, tends to produce the most reliable bite for most coastal species. Steady high pressure (1020–1030 hPa, unchanged) is decent but unremarkable. The most intense but short-lived bite often occurs in the 3–6 hours before a front arrives — when pressure is dropping fast (4+ hPa / 12h).
• Does barometric pressure really affect fishing?
  Yes — there is evidence from both field observation and catch-log analysis. The mechanism is the swim bladder: most bony fish have a gas-filled organ they use to maintain neutral buoyancy. When external pressure drops rapidly, the gas in the swim bladder expands, creating discomfort. Fish respond by moving to shallower water and feeding aggressively. Cartilaginous fish (sharks, rays) that lack swim bladders are less affected by pressure change.
• What is a "fishable" barometric reading?
  The rate of change matters more than the absolute value. A rapid drop of 4+ hPa in 12 hours means a front is approaching: fishing is typically active. A slow drop of 1–2 hPa over 24 hours is usually inconclusive. A steady reading (±1 hPa over 12 hours) at any level tends to produce consistent if unexciting fishing. A rapid rise (4+ hPa / 12h after a front passes) is typically the best sustained bite of the week.